Fig 8.

T-cell proliferation. Fifteen Swiss-Webster mice were challenged i.n. with 170 CFU (0.5 LD₅₀) of either the WT or Δlpp msbB CO92 strain (30 mice total). At 14 (A), 21 (B), and 60 (C) days p.i., spleens from 5 mice in each infected group (at each time point) were harvested. T cells were isolated from each animal separately and incubated with γ-irradiated APCs either stimulated (pulsed) with heat-killed WT Y. pestis CO92 or without stimulation (unpulsed). T-cell proliferation was measured by [³H]thymidine incorporation. Data were analyzed by one-way ANOVA with the Holm-Sidak method, and statistically significant differences are indicated by lines with P values. The error bars indicate standard deviations.